Digital Batteries Alfred W. Hubler and Onyeama Osuagwu

1

• Digital Batteries
• Alfred W. Hubler and Onyeama Osuagwu
• Center for Complex Systems Research, UIUC
• hubler.alfred_at_gmail.com
• We study arrays of solid state nano junctions
• where charge recombination is quantum-
• mechanically forbidden
• where each capacitor can be individually
  charged/discharged, as in a flash drive
• where design prevents tunneling, even if the
  energy density is very high
• which can be integrated on the wafer with
  sensors, CPUs
• which have an energy density gt 1 GJ/m3 (200
  kJ/kg), charging-discharging rates in the THz
  range, and exceed number of charging cycles of
  chemical batteries and conventional capacitors by
  orders of magnitude.
• which are fully operational in a large
  temperature range (from -273oC to 500oC) and have
  no thermal run-away
• We find
• - main problem SiO2 compressive strength of 1
  GPa limits energy density to 200 kJ/kg
• http//www.physics.uiuc.edu/people/Hubler/
  http//server10.how-why.com/blog/

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Energy storage in conventional capacitors Capacit
ors are environmentally friendly, work in a large
temperature range (0K-melting temperature of
metal ), and have a virtually unlimited number
of charging cycles. The energy stored in a
capacitor is W ½ C V2 ,
(1) where Ce A / d is the capacity, V applied
voltage, e electric constant, A plate area, d
plate distance The energy density is
w ½ e E2 ,
(2)
Where the electric field, E V/d
However, if the
energy density in conventional
capacitors exceeds E3
x 106V/m in air (6 x
107V/m in Teflon) the capacitor
discharges by
arcing and the energy is lost. gt
Theoretical
value of maximum energy density is
small,
w 100 KJ/m3
(500J/kg)
Conventional capacitors need a long time (t

) to charge/discharge since
inductance
L is large.
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Energy storage in chemical batteries, hydrogen
fuel cells, and gasoline Energy stored in
chemical systems is stored as electrostatic
energy, as in capacitors. But, in chemicals such
as hydrogen, the limiting electric fields are
much higher. Quantization phenomena at the atomic
level prevent charge recombination gt high
energy density. Atomic hydrogen is a good
example. Energy could be stored in a hydrogen
atom by lifting the electron from the ground
state to the highest excited state (ionization).
In this case, the ratio between the stored energy
and the volume of the atom is w 13.6eV /
(volume of hydrogen atom) 3.3 x 1013J / m3
(1.31 x 1012J/kg) i.e. nine orders of magnitude
above the maximum energy density in a
conventional capacitor. Since the excited state
of hydrogen atoms is short lived, hydrogen atoms
cannot be used for long term energy storage. For
this reason, hydrogen moleculesand
carbohydrates, such as gasolineare commonly used
for energy storage. Unfortunately, molecular
hydrogen is difficult to handle and the energy
retrieval from hydrogen and carbohydrates in fuel
cells is slow and inefficient, works only in a
small temperature range, and experimental energy
density ltlt limit. Energy storage in faradic
systems has low efficiency and is limited by
diffusion, reaction rates, fractal growth
irreversible chemical reactions.
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• Digital batteries
• We model arrays of nano-scale solid state
  junctions
• where
• field emission, avalanche breakdown and Zener
• breakdown are prevented by quantization
  phenomena,
• and which are similar to
• LEDs and laser diodes, but without charge
• recombination or tunneling,
• Magnetic tunneling junctions, but much simpler in
  
• design and cheaper to build
• This work builds on our Correlation Tunnel Device
  patent 1, and is ready for publication.
• 1 H. Higuraskh, A. Toriumi, F. Yamaguchi, K.
  Kawamura, A. Hübler, Correlation Tunnel Device,
  U. S. Patent 5,679,961 (1997)

Nano-capacitors are similar to LEDs, except that
they store energy instead of converting it to
light
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Digital batteries We find Nano-junction arrays
could sustain energy densities up to
10MJ/kg without significant
charge recombination, however the compressive
strength of the materials (1GPa for SiO2)
limits the energy density to Emax
compressive-strength / density
200 kJ/kg (for SiO2 substrates) The
charge discharge rate is limited by the
induction f junction-size
/ speed-of-light which is in the THz range. The
energy density of chemical batteries is less than
1 kJ/kg. The charge discharge rate of batteries
is limited by diffusion and reaction rates.
Nano-capacitors are similar to LEDs, except that
they store energy instead of converting it to
light
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Nano-junction arrays as Digital Batteries One
could design large arrays of individually
connected nano-junction, which could be charged
and discharged one-by-one, similar to flash drive
technology. In contrast to conventional
batteries, the output voltage would remain
constant until the last nano-capacitor is
discharged and charging/discharging digital
batteries would be orders of magnitude faster.
Such arrays of nano-capacitors could serve as
digital batteries. Digital batteries would
produce a stable output voltage, making them
ideal for sensors and other sensitive
devices. Digital batteries could be recharged
probably millions of times, whereas chemical
batteries can be recharged only a few thousand
times.
Digital batteries are similar to flash drives
flash drives store charge, while digital
batteries store energy
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• Conclusion
• Digital batteries are potentially an inexpensive
  and
• environmentally-friendly alternative to both
  chemical
• Batteries.
• Digital batteries are arrays of solid state nano
  junction
• where charge recombination is quantum-
• mechanically forbidden
• where each capacitor can be individually
  charged-
• discharged, as in a flash drive
• where design prevents tunneling, even if the
  energy
• density is very high
• which can be integrated on the wafer with
  sensors, CPUs
• which have high energy density, up to 1 GJ/m3
  (200 kJ/kg), charging-discharging rates in the
  THz range, and exceed number of charging cycles
  of chemical batteries and conventional capacitors
  by orders of magnitude.
• which are fully operational in a large
  temperature range (from -273oC to 500oC) and have
  no thermal run-away
• - main problem SiO2 compressive strength 1
  GPa (200 kJ/kg)
• http//www.physics.uiuc.edu/people/Hubler/
  http//server10.how-why.com/blog/

Digital batteries are similar to flash drives
flash drives store charge, while digital
batteries store energy